Small flash-memory cards have become wildly popular and have replaced floppy disks for data transport. Falling prices and advances in technology for flash-memory chips have allowed for larger memory capacities in multiple, diverse form factors, while advances in chip packaging have allowed for smaller physical sizes of flash-memory cards.
A flash-memory chip may be soldered to a printed-circuit board (PCB) or a flex carrier substrate that is then encased in a plastic shell that exposes metal contacts. The metal contacts make contacts with a connector plug when the flash-memory card is plugged into a host, such as a personal computer (PC), cell phone, digital camera, or other computing device. A flash controller may be integrated with the flash-memory chip, or may be a separate chip soldered to the PCB or flex carrier. For writes, the flash controller receives commands, address, and data carried from the host over a host bus to the metal contacts, and sends corresponding control, address, and data signals to the flash-memory chip.
A number of protocols are used for the host bus, and standards have been developed that specify the physical dimensions of the device as well as the host-bus protocol. Older standards such as compact-flash (CF) specified large, thick devices, while more recent standards such as Secure Digital (SD) and Sony's Memory Stick significantly reduced the device thickness.
Further improvements in packaging and device construction have enabled even smaller flash-memory cards. An extension of SD known as microSD yields a flash-memory card about the size and thickness of a US dime coin, although the microSD card is rectangular and lighter than the dime. An extension of Sony's Memory Stick, known as a Memory Stick Micro (M2) is similar in size and thickness.
FIG. 1 shows several prior-art flash-memory cards. SD card 36 is a Secure Digital (SD) card that has a series of metal contacts 14 exposed along one edge. Metal contacts 14 mate with socket contacts in a host when SD card 36 is inserted into a host. Metal contacts 14 include power, ground, and other signals such as data lines, a clock, command, and card-detect signals.
Memory Stick 38 is a Memory Stick Duo or PRO Duo flash-memory card. SD card 36 and Memory Stick 38 are mid-generation devices and are larger in size, being roughly an inch in length and about 2 mm in thickness.
Newer-generation devices include Memory Stick Micro 32 (M2) and microSD card 34. These devices are about a quarter of the size of earlier-generation cards, such as SD card 36 and Memory Stick 38. MicroSD card 34 has a reduced thickness of only 1 mm, while Memory Stick Micro 32 is 1.2 mm in thickness. Metal contacts 16 are smaller, and may have longer contacts for power and ground to connect power and ground before other signals are connected during insertion.
FIG. 2 highlights a problem with the smaller flash-memory cards. The extremely small size of microSD card 34 (the size of a fingernail) makes accidental loss of the card more likely than for the larger cards. MicroSD card 34 could slip out of a person's hand, or pass through a small hole in a person's pocket without notice. Memory Stick Micro 32 or microSD card 34 could easily be lost on a messy desk at work or at home.
Loss of a flash memory card is quite undesirable, not just due to the cost of the flash device itself. The data stored on the flash memory card may be critical data. Loss of such critical data may lead to identity theft or compromised trade secrets. Address and phone lists of customers could be useful to a competitor. A spammer may use a list of email addresses found on a lost flash-memory card, to the embarrassment of the owner of the lost flash-memory card.
MicroSD card 34 could be inserted into an adapter for a larger format, such as an adapter between microSD card 34 and SD card 36. However, the size of SD card 36 is still somewhat small. Credit-card-sized carriers are available for carrying a car key in a person's wallet for emergencies, and a similar carrier could be used for carrying SD card 36 in a wallet. However, the many standards for micro flash-memory cards make a multi-standard wallet carrier more desirable.
What is desired is a multi-standard carrier that fits in a person's wallet. A multi-standard carrier that can carry multiple kinds of flash-memory cards is desirable. A multi-standard carrier that has a size similar to a credit card is desirable so that the carrier could be placed into a person's wallet in place of a credit card. A credit-card-sized carrier is desirable for transporting micro flash-memory cards so that the micro flash-memory cards are not lost during transport.